Formulation of phosphorus fertilizer for plants

ABSTRACT

Concentrated phosphorus fertilizers are disclosed that comprise a buffered composition of an organic acid and salts thereof and a phosphorous-containing acid and salts thereof. The concentrated phosphorus fertilizers can be diluted with water of pH ranging from about 6.5 to about 8.5 at ratios of concentrate to water at about 1:40 to about 1:600 to result in a fertilizer having a pH in the range acceptable for foliar uptake of phosphorus.

This is a continuation of application Ser. No. 09/126,233, filed Jul.30, 1998, now U.S. Pat. No. 6,113,665 which is a continuation ofapplication Ser. No. 08/642,574, filed May 3, 1996, now U.S. Pat. No.5,830,255, re-examined as U.S. Pat. No. B1 5,830,255 (certificate issuedJul. 11, 2000), which is a continuation of application Ser. No.08/192,508, filed Feb. 7, 1994, now U.S. Pat. No. 5,514,200.

BACKGROUND OF THE INVENTION

Fertilizers are added to the soil of crops or in some cases they can beapplied directly to crop foliage to supply elements needed for plantnutrition. Seventeen elements are known to be essential to the healthand growth of plants. Typically, nitrogen, phosphorus, and potassium areprovided in the greatest quantity. With increasing knowledge of the roleof each of the nutrients essential to plants, there is a betterunderstanding of the importance of providing a given nutrient at theappropriate stage of phenology. To accomplish this, rapid changes infertilizer formulations and methods of application have been necessary.

Another factor changing fertilization formulations and methods is due topressure from federal, state and local regulatory agencies and citizengroups to reduce the total amount of fertilizer in general, and ofspecific nutrients in particular, being applied to the soil.Additionally, the loss of registration of existing synthetic plantgrowth regulators and organic pesticides and the prohibitively highcosts involved in the successful registration of new ones, also plays arole in the changing arena of crop fertilization.

The principal source of phosphorus for the fertilizer industry isderived from the ores of phosphorus-containing minerals found in theEarth's crust, termed phosphate rock. Elemental phosphorus does notexist in nature; plants utilize phosphorus as the dihydrogen phosphateion (H₂PO₄). While untreated phosphate rock has been used forfertilizer, it is most commonly acidulated with dilute solutions ofstrong mineral acids to form phosphoric acid, which is more readilyabsorbed by crops.

Until recently, phosphate and polyphosphate compounds were consideredthe only forms in which phosphorus could be supplied to plants to meetthe plant's nutritional need for phosphorus. Indeed, the only phosphitecompound cited for use as a fertilizer in the Merck Index (M. Windhols,ed., 1983, 10th edition, p. 1678) is calcium phosphite (CaHPO₃). Nophosphite fertilizer formulations are listed in The Farm ChemicalHandbook (Meister Publishing Co., 1993, Willoughby, Ohio 834 p.) orWestern Fertilizer Handbook (The Interstate, Danville, Ill. 288 p.)Historically, calcium phosphite was formed as a putative contaminant inthe synthesis of calcium superphosphate fertilizers [Mcintyre et al.,Aaron. J. 42:543-549 (1950)] and in one case, was demonstrated to causeinjury to corn [Lucas et al., Agron. J. 71:1063-1065 (1979)].Consequently, phosphite was relegated for use only as a fungicide(Alliete®; U.S. Pat. No. 4,075,324) and as a food preservative.

More recently, it has been shown that plants can obtain phosphorus fromphosphite [Lovatt, C. J., Mar. 22, 1990, “Foliar phosphorusfertilization of citrus by foliar application of phosphite” In: CitrusResearch Advisory Committee (eds) Summary of Citrus Research, Universityof California, Riverside, Calif. pp 25-26; Anon., May, 1990, “Foliarapplications do double duty” In: L. Robison (ed) Citrograph Vol. 75, No.7, p 161; Lovatt, C. J., 1990, “A definitive test to. determine whetherphosphite fertilization can replace phosphate fertilization to supply Pin the metabolism of ‘Hass’ on ‘Duke 7’:—A preliminary report”California Avocado Society Yearbook 74:61-64; Lovatt, C. J., 1992].Formulations based on phosphorous acid and hypophosphorous acid, asphosphite is, generally undergo oxidation to phosphate and thus lose thebenefits that could be derived from the use of phosphite fertilizationapplications.

The phosphate and polyphosphate fertilizers currently used have a numberof properties that compromise their desirability as fertilizers.Generally, they tend to form precipitates during storage and shipping.This limits the ability to formulate concentrated solutions offertilizers. Additionally, formulations must generally be maintained ata narrow pH range to prevent precipitation, resulting in fertilizersthat are limited to particular uses.

Another drawback of phosphate fertilizers is that they are not readilytaken up by the foliage of many plants and must instead be delivered tothe soil for uptake by plant roots. The mobility of phosphatefertilizers in the soil is limited leading to rapid localized depletionof phosphorus in the rhizosphere and phosphorus deficiency of the plant.Frequent reapplication of phosphate fertilizers is undesirable becauseit leads to leaching of phosphate into the groundwater resulting ineutrophication of lakes, ponds and streams.

Phosphate and polyphosphate fertilizers have also been shown to inhibitthe beneficial symbiosis between the roots of the plants and mycorrhizalfungi. They tend to support the growth of algae and promote bacterialand fungal growth in the rhizosphere, including the growth of pathogenicfungi and other soil-borne pests.

Even though phosphorus, once in the plant, is very phloem mobile (i.e.readily moving from old leaves to young tissues), phosphate is poorlyabsorbed through the leaves of most plant species. This is unfortunatebecause successful foliar phosphorus feeding would result in theapplication of less phosphate fertilizers to the soil and reducephosphorus pollution of the ground water.

Accordingly, there is a need for a phosphorus fertilizer that can beutilized in irrigation systems and applied to foliage without theformation of precipitates that reduce nutrient availability and uptakeby the plant and plug emitters and sprayers. There is also a need fornew methods of fertilizer application that allow nutrients in a readilyavailable form to be supplied at the exact time the plant needs them.This need includes the facility of a foliar product to be sold in asingle formulation for use as a concentrated material for airplane orhelicopter application or as a dilute solution for ground sprayapplication and yet able to be maintained at a suitable pH range optimalfor leaf uptake despite the need to be diluted prior to application.

Additionally, there is a demand for phosphorus fertilizers that have thefacility to be used as liquids or solids (granule or powder). There isalso a demand for fertilizers that do more than just supply nutrients.It is desired that the fertilizers also have demonstrated plant growthregulator activity, increase the plants' resistance to pests, promoteplant health in general and root health in particular, increase theproduction of allelopathic compounds, increase pre- and post-harvestquality, improve stress tolerance, enhance beneficial symbioses, andimprove yield over existing traditional soil or foliar fertilizers.

SUMMARY OF THE INVENTION

Given the above-mentioned deficiencies and demands of fertilizers ingeneral, and of phosphorus fertilizers in particular, it is an object ofthe present invention to provide phosphorus to plants in a formulationthat renders phosphorus readily available to the plants under a numberof application methods such as through soil, foliar uptake, irrigation,and other methods.

It is also an object that the phosphorus fertilizer formulations beconveniently formulated in concentrated solutions that are stable duringstorage and shipping.

Another object of the present invention is to provide a phosphorusfertilizer that is not as inhibitory to mycorrhizal fungi as traditionalphosphate fertilizers.

It is a further object of the present invention to provide a phosphorusfertilizer that does not support the growth of algae to the same degreethat traditional phosphate fertilizers do.

Additional objects and features of the invention will be apparent tothose skilled in the art from the following detailed description andappended claims.

The above objects and features are accomplished by a concentratedphosphorus fertilizer comprising a buffered composition comprising anorganic acid and salts thereof and a phosphorous-containing acid andsalts thereof. The concentrated phosphorus fertilizer can be dilutedwith water of pH ranging from about 6.5 to about 8.5 at ratios ofconcentrate to water at about 1:40 to about 1:600 to result in a fullysolubilized fertilizer having a pH in a range acceptable for foliaruptake of phosphorus.

In one embodiment, the phosphorous-containing acid is selected from thegroup consisting of phosphorous acid, hypophosphorous acid,polyphosphorous acid, and polyhypophosphorous acid and the organic acidis preferably selected from the group consisting of dicarboxylic acidsand tricarboxylic acids such as citrate.

In one embodiment, the concentrated phosphorus fertilizer is anessentially clear liquid devoid of precipitate that can be diluted at aratio of about 1:40 to about 1:600 with water having pH of about 6.5 toabout 8.5, to result in a fertilizer having a pH of about 5.0 to about7.0, and more preferably from about 5.5 to about 6.5, to facilitate theuptake of phosphorus by a variety of plants.

A method of providing phosphorus to plants is also disclosed. The methodcomprises diluting a concentrated phosphorus fertilizer comprising abuffered composition comprising an organic acid and salts thereof and aphosphorous-containing acid and salts thereof with water to form asubstantially fully solubilized use-dilution fertilizer having a pH in arange acceptable for foliar uptake of phosphorus, and applying thefertilizer to the plant foliage.

DETAILED DESCRIPTION OF THE INVENTION

The present invention provides phosphorus fertilizers essentially devoidof phosphate. The fertilizer comprises a double or multiple buffersystem of organic acids and their salts with a phosphorous-containingacids and their salts. The formulation stabilizes the phosphorousagainst oxidation to phosphate. Suitable phosphorous-containing acidsare phosphorous acid and polyphosphorous acid, based generally on theformula H₃PO₃, and hypophosphorous acid and polyhypophosphorous acid,based generally on the formula H₃PO₂. Phosphite, the salt of phosphorousacid, has properties that are known to be beneficial to crop production.It is taken up through the foliage of avocado and citrus, two specieswhich classically do not take up phosphate through their foliage.Phosphite has fungicidal properties with regard to some species ofpathogenic fungi: Rhizoctonia solani, Botrytis cinerea, Piriculariaoryzae, Plasmopora viticola, Phytophthora cinnamomi, andPhytophthoraparasitica. Recently, it has been demonstrated thatphosphite also serves as a source of metabolically active phosphorus inplants. The properties of phosphite that make it desirable as afertilizer are enhanced when it is formulated according to the presentinvention as a double or multiple buffer with phosphorous acid,hypophosphorous acid, polyphosphorous acid and/or polyhypophosphorousacid and their respective salts and organic acids and their salts perthis invention.

Suitable organic acids have the formula R—COOH or R—COO⁻ where R ishydrogen or a carbon-containing molecule or group of molecules. Suitableorganic acids are those that maintain the phosphite ion in asubstantially fully solubilized form upon dilution with water at pHvarying from about 6.5 to about 8.5 and that result in a use-dilutionfertilizer having a foliage acceptable pH for phosphorus uptake.Preferred organic acids are dicarboxylic and tricarboxylic acids.

By the term “substantially fully solubilized” it is meant that upondilution, the phosphite does not precipitate, or at least notappreciably, so as to affect administration of the liquid product to theplant foliage, and thus is in a form available to the plant. Withpresent phosphite fertilizers, there is a tendency for phosphite toprecipitate if diluted with alkaline water, thereby rendering thephosphite in a form that is unavailable to the plant for uptake. By theterm “foliage-acceptable pH for phosphorus uptake”, it is meant a pHthat allows phosphorus to be absorbed by the plant without causingdamage to the foliage. A foliage-acceptable pH for phosphorus uptakeusually ranges between about 5.0 to about 7.0, and preferably betweenabout 5.5 to about 6.5. Phosphorus is most readily taken up by foliageat pH 6.0. Depending on the plant species, a pH below 5.0 can causedamage to leaves and/or the flowers and/or fruit. At higher pH, betweenabout 7.0 to about 7.5, there is reduced uptake of nutrients, althoughgenerally there is no plant damage. A pH between about 7.5 and 8.0,depending on the plant species, plant damage may result. A pH greaterthan 8.0, generally causes damage to the plant in addition to reducinguptake of the nutrients. Accordingly, suitable organic acids are thosethat help provide a “buffered composition” having the desired pH range.This means that a “use-dilution fertilizer” having an acidic to neutralpH (pH 5.0 to 7.0) can be achieved upon high dilutions (up to about1/600) of the concentrated fertilizer with highly alkaline water (up toa pH of about 8.5).

Organic acids that meet this criteria include but not limited tointermediates in the Kreb's Tricarboxylic Acid Cycle, amino acids suchas glutamic acid and aspartic acid, vitamin acids such as ascorbic acidand folic acid, and their respective salts. Particularly preferredorganic acids are dicarboxylic and tricarboxylic acids selected from thegroup consisting of citrate, pyruvate, succinate, fumarate, malate,formate, oxaloacetate, citrate, cis-aconitate, isocitrate, anda-ketoglutarate. Citrate is a particularly preferred organic acidbecause of it is relatively inexpensive and readily available.

These formulations allow the maintenance of continued solubility, andthus availability for uptake by plants, of phosphorus, with or withoutother nutrients, over a significantly wide range of concentrations andpHs. The increased solubility of these formulation over that ofphosphate or phosphite fertilizers makes it possible to preparefertilizers with a greater concentration of phosphorus per unit volumethan traditional phosphate or polyphosphate fertilizers or the simpleunbuffered salts of phosphorous acid recently being marketed asfertilizers for foliar application which are available as supersaturated solutions with only about 16% phosphite, and which are dilutedapproximately 1:100 to about 1:300. The resulting pH of thesefertilizers varies significantly depending upon the pH of the waterused, thus affecting the availability of the nutrients for foliaruptake. In contrast, the highly concentrated fertilizers of the presentinvention, which can be diluted with water at a ratio of about 1:600,allow for more cost effective shipping, handling, and application. Theyresult in greater uptake of phosphorus by the canopy of plants thantraditional phosphate or recent phosphite fertilizers not formulated inthis manner.

The formulations provided herein also make it possible to formulatevarious combinations of other essential plant nutrients or otherinorganic or organic compounds as desired and maintain their solubilitywhen used over a wide range of concentrations and pHs, which is notpossible for present phosphate or phosphite fertilizers. For example,boron, manganese, calcium, iron and other elements can be provided atrelatively high concentrations in these formulations. Thus, thesephosphorus fertilizers also enhance the canopy uptake of other mineralnutrients essential to plants. They can be used as a canopy applicationto improve pre- and post-harvest crop quality.

Formulations can also prepared with copper. However, when highconcentrations of copper are used, the copper is not fully solubilized.In this situation, the insoluble copper is desirable as it preventsrapid uptake of the copper and thus minimizes the potential for coppertoxicity. As the insoluble copper is rewetted over night by dew,dissolution occurs so. that additional copper is taken up. The bufferingcapacity of the formulation maintains the pH at a foliage-acceptable pHwhen the insoluble copper is rewetted so that conditions are optimal foruptake and are benign to the plant tissues. While copper is an elementessential to plants, it is required in only small amounts. In relationto nitrogen, plants require, in general, 10,000- to 75,000-fold lesscopper. Provided to the foliage of the plant at the rate provided bythis formulation, copper is a very effective fungicide, in addition tobeing a plant nutrient and fertilizer.

In addition to the above-mentioned advantages, the formulationsdisclosed have a direct benefit to the environment. Because theformulations allow successful foliar feeding of phosphorus to a numberof plants that do not effectively take up phosphorus when supplied inphosphate or polyphosphate forms, and because these formulations enhancethe uptake of other nutrients, they are cost-effective and can replaceless efficient, traditional soil-feeding methods. This results inreducing phosphate pollution of the groundwater and eutrophication offreshwater ponds, lakes and streams.

The phosphorus fertilizers disclosed herein can also be advantageouslyapplied through the soil or by irrigation systems as solid (granular) orliquid formulations. These formulations can be used at pHs sufficientlylow to clean irrigation lines and alter the pH of the soil to solvealkalinity problems while supplying essential nutrients to plants.Example 2, below discloses a suitable formulation for irrigationapplication. With irrigation application, the fertilizer flowing throughthe irrigation system will typically have a pH lower than about 2.5,usually less than about pH 1.5. The low pH is designed to supplyphosphorus while killing bacteria and algae (slime) which plugirrigation lines, thus cleaning the lines. The low pH also dissolvescalcium carbonate deposits at and around the emitters, and solubilizesthe calcium carbonate so Ca²⁺ is available to the plant. Once deliveredto the soil near the plant, sufficient water is applied to achieve a pHsuitable for phosphorus uptake by the plant. The form in which thephosphorus is supplied in these formulations is more mobile thanphosphate fertilizers or than the simple salts of phosphorous acidrecently being sold as fertilizers, and thus more available and morereadily taken up by the roots of plants. An advantage of theseformulations is that the form in which phosphorus is supplied does notinhibit the development of mycorrhizal fungi to the same degree thattraditional phosphate fertilizers do. The present compositions can alsobe formulated with certain nutrients in addition to phosphorus that arereadily absorbed through soil applications at pH of about 5.5 to about7.0. Such nutrients include nitrogen, calcium, magnesium, potassium,molybdenum, boron, and sulfur.

Another advantage with the phosphorus fertilizers disclosed herein isthat they do not support the growth of green algae to the same degreethat traditional phosphate fertilizers do. This is of significantimportance to agriculture, commercial nurseries, the ornamental and cutflower industry, and the home and garden industry, as it will preventthe growth of green algae which typically proliferate and plugirrigation emitters, foul pots and benches, and provide a niche for thegrowth of pathogenic bacteria and fungi. These formulations also endowthe phosphorus fertilizer with anti-viral, anti-bacterial andanti-fungal activity. This bacterialcidal activity in a phosphorusfertilizer makes it possible to use this fertilizer to inhibitice-nucleating bacteria to thus protect plants from frost damage.

Methods of Preparation

The phosphorus fertilizers are prepared by first forming solutions ofthe phosphorous and organic acids. Other desired nutrients can then beadded with constant stirring. The amount of phosphorous relative toorganic acid is not critical, as long as appropriate buffering andsolubility are achieved. Generally the amount of organic acid that isadded will depend upon the form in which the nutrient elements areadded. For example, if calcium is to be added in the form of calciumhydroxide (a base), then the acid form of the organic acid, for examplecitric acid, would be used rather than its salt, citrate. In addition tothe desired nutrients, other additives, that are known in the fertilizerindustry, can be added. These include, for example, wettingagents,surfactants, spreaders, stickers etc., and are described in The FarmChemical Handbook, supra (incorporated herein by reference). Thefertilizer compositions can also be prepared as solid formulations,identical to the liquid ones by simply leaving out all of the water. Theproperties are the same as the liquid formulations but have theadditional advantage of weighing less for the same amount of nutrient.

Methods of Application

The fertilizer is applied according to crop-specific recommendationswhich will depend upon the application method (foliar, soil, irrigation,etc.), time of application, rate of application, and productformulation. Crops that will benefit from the fertilizer include, butare not limited to, avocado, citrus, mango, coffee, deciduous treecrops, grapes and other berry crops, soybean and other commercial beans,corn, tomato, cucurbits and cucumis species, lettuce, potato, sugarbeets, peppers, sugarcane, hops, tobacco, pineapple, coconut palm andother commercial and ornamental palms, hevea rubber, and ornamentalplants.

In addition to the foliar, soil, and irrigation application methodsmentioned above, the present fertilizer may prove beneficial to certaincrops through other application methods. For example, trunk paints orother methodologies may provide for a continuous low supply offertilizers, such as, for example, “intravenous” feeding as practiced inthe boron nutrition of soybeans.

In order that the invention described herein may be more fullyunderstood, the following examples are set forth. All chemicals usedwere of analytical reagent quality and approximately 100% by weightunless otherwise specified. All formulations are expressed in terms ofweight to volume. It should be understood that these examples are forillustrative purposes only and are not to be construed as limiting thescope of the invention in any manner.

EXAMPLE 1

A formulation was prepared of 1 gallon of 0-40-0 fertilizer with 3.86lbs H₃PO₃, 1.34 lbs tripotassium citrate, 1.34 lbs of trisodium citrate,and 4.0 lbs of 58% ammonium hydroxide. The components were dissolved inwater with constant stirring. This single formulation can be used at arate of 2 quarts in as little as 20 gallons of water of pH 6.5 to 8.5 upto 300 gallons of water of pH 6.5 to 8.5 and maintain a pH between 5.5to 6.5 without the formation of any precipitate.

EXAMPLE 2

A formulation was prepared of 1 gallon of 0-40-0 fertilizer with 3.86lbs H₃PO₃ and 0.5 lbs citric acid. This formulation is stable at pH 1.0or less and is designed for application through the irrigation system.It is stable against oxidation and precipitation when supplied throughthe irrigation water.

EXAMPLE 3

A formulation was prepared of 1 gallon of 0-30-0 fertilizer with 74.89%elemental boron with 2.89 lbs H₃PO₃, 28.67 lbs borax (Na₂B₄O₇.10 H₂O),17.16 lbs boric acid (H₃BO₃), 1.54 lbs H₂SO₄ and 2.67 lbs citric acid. Asolution of the phosphorous and citric acid was first prepared, then theother elements were added with constant stirring. This formulation canbe used at the rate of 2 quarts in as little as 20 gallons of water ofpH between 6.5 to 8.5 up to 300 gallons of water of pH 6.5 to 8.5 andmaintain a pH between 5.5 to 6.5 without the formation of anyprecipitate.

EXAMPLE 4

A formulation was prepared of 1 gallon of 0-30-0 fertilizer with 21.57%Zn and 23.22% Mn with 2.89 lbs of H₃PO₃, 7.92 lbs ZnSO₄, 7.16 lbsMn(H₂PO₂)₂.H₂O, 0.61 lbs citric acid and 0.87 lbs 58% NH₄OH. Thisformulation can be used at the rate of two quarts in as little as 20gallons of water of pH between 6.5 to 8.5 up to 300 gallons of water ofpH between 6.5 to 8.5 and maintain a pH between 5.5 to 6.5 without theformation of any precipitate.

EXAMPLE 5

A formulation was prepared of 1 gallon of 0-30-0 fertilizer with 5.4%Ca. It was packaged in a two-container system where 1 gallon of solutionA contained 2.89 lbs H₃PO₃, 0.68 lbs Ca(OH)₂, and 0.28 lbs citric acid,and 1 gallon of solution B contained 0.16 lbs Ca(OH)₂, 0.60 lbs KOH,3.34 lbs 58% NH₄oH, 0.28 lbs citric acid, and 0.67 lbs EDTA(ethylenediaminetetraacetic acid). Two quarts of solution A can be addedto as little as 20 gallons of water of pH between 6.5 to 8.5 up to 300gallons of water of pH between 6.5 to 8.5 followed by the addition oftwo quarts of solution B. The final solution is between pH 5.5 to 6.5and without precipitation.

A formulation of 1 gallon of 0-30-0 fertilizer with 4.32% Ca can be madewithout requiring EDTA. This formulation is also packaged in atwo-container system where 1 gallon of solution A contains 2.89 lbsH₃PO₃, 0.67 lbs Ca(OH)₂ and 0.28 lbs of citric acid, while 1 gallon ofsolution B contains 2.67 lbs of 58% NH₄OH, 0.6 lbs KOH. Two quarts ofsolution A can be added to as little as 20 gallons of water of pHbetween 6.5 to 8.5 up to 300 gallons of water of pH between 6.5 and 8.5followed by the addition of two quarts of solution B. The final pH ofthe solution is between 5.5 and 6.5 and without precipitation.

EXAMPLE 6

A formulation was prepared of 1 gallon of 0-30-30 fertilizer with 2.89lbs H₃PO₃, 2.99 lbs KOH, and 0.84 lbs citric acid. Two quarts can beadded to as little as 20 gallons of water of pH between 6.5 to 8.5 andup to 300 gallons of water of pH between 6.5 and 8.5. The pH of thefinal solution is between 5.5 and 6.5 without precipitation.

EXAMPLE 7

A formulation was prepared of 1 gallon of 0-30-0 fertilizer having 4.8%iron with 2.89 H₃PO₃, 1.75 lbs iron-citrate, 0.74 lbs KOH, 0.62 lbsNaOH, and 2.00 lbs of 58% NH₄OH. Two quarts of the formulation can beadded to as little as 20 gallons of water pH 6.5 to 8.5 and up to 300gallons of water of pH 6.5 to 8.5. The pH of the final solution isbetween 5.5 to 6.7 without precipitation.

EXAMPLE 8

A formulation was prepared of 1 gallon of 0-30-0 fertilizer having23.22% manganese with 2.89 H₃PO₃, 7.16 lbs. Mn(H₂PO₂)₂, and 0.133 lbs.sodium citrate. Two quarts of the formulation can be added to as littleas 20 gallons of water pH 6.5 to 8.5 and up to 300 gallons of water ofpH 6.5 to 8.5. The pH of the final solution is between 5.5 to 6.5without precipitation.

EXAMPLE 9

A formulation was prepared of 1 gallon of 0-30-0 fertilizer having 57%copper with 2.89 H₃PO₃, 7.3 lbs Cu(OH)₂ (57% Cu), and 1.34 lbs of 58%NH₄ 0H. Two quarts can be added to as little as 20 gallons of water ofpH 6.5 to 8.5 up to 300 gallons of water of pH 6.5 to 8.5. The pH of thefinal solution is between 5.5 to 6.5. The copper is not fully soluble,however this is desirable in that it prevents the rapid uptake of copperwhen applied to plant foliage.

1. A concentrated phosphorus fertilizer for irrigation application, saidfertilizer comprising a buffered composition comprising aphosphorous-containing acid selected from the group consisting ofphosphorous acid, hypophosphorous acid, polyphosphorous acid,polyhypophosphorous acid and salts thereof, wherein saidphosphorous-containing acid or salt thereof is present in an amount ofabout 30 weight percent or greater, said composition having a pH lessthan about 2.5.
 2. The phosphorus fertilizer of claim 1 having a pH ofless than about 1.5.
 3. The concentrated phosphorus fertilizer as inclaim 1 wherein said phosphorous-containing acid or salt thereof ispresent in amount of about 30 weight percent to about 46 weight percent.4. A method of providing phosphorus to a plant comprising distributing aliquid concentrated phosphorus fertilizer comprising a bufferedcomposition comprising a phosphorous-containing acid selected from thegroup consisting of phosphorous acid, hypophosphorous acid,polyphosphorous acid, polyhypophosphorous acid and salts thereof,wherein said phosphorous-containing acid or salt thereof is present inan amount of about 30 weight percent or greater, through an irrigationsystem and delivering said fertilizer to soil near said plant, saidfertilizer having a pH less than about 2.5.
 5. The method of claim 4wherein said fertilizer has a pH less than about 1.5.
 6. The method asin claim 4 wherein said phosphorous-containing acid or salt thereof ispresent in an amount about 30 weight percent to about 46 weight percent.